To make it a suitable replacement for ctb in my book it would need the following features:
- update metadata on opening book (lastread entry)
- ability to sort on lastread and lastadded
- ability to make one of the above the default sort method

I realize though this might defeat the purpose of the program, as it was meant to be a replacement for an indexed file browser. So feel free to ignore this. I'm actually quite happy with ctb except for its inefficient use of screen space.